Intramolecular OH⋅⋅⋅Fluorine Hydrogen Bonding in Saturated, Acyclic Fluorohydrins: The γ-Fluoropropanol Motif.
Intramolecular OH⋅⋅⋅Fluorine Hydrogen Bonding in Saturated, Acyclic Fluorohydrins: The γ-Fluoropropanol Motif.
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DOI：
10.1002/chem.201503253
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发表时间：
2015-12-01
期刊：
影响因子：
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通讯作者：
Graton J
中科院分区：
文献类型：
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作者：
Linclau B;Peron F;Bogdan E;Wells N;Wang Z;Compain G;Fontenelle CQ;Galland N;Le Questel JY;Graton J
氟化通常用于化合物性能优化。然而，氟化对相邻官能团氢键（HB）性质的影响以及氟本身的HB接受能力仍不完全清楚。尽管构象限制的氟代醇可以形成 OH⋅⋅⋅F 分子内 HBs (IMHBs)，但柔性化合物中的这种相互作用仍然存在疑问。与之前的报道相比，本文首次证明了无环饱和 γ-氟代醇中存在 OH····F IMHB，甚至对于母体 3-氟丙-1-醇也是如此。相对立体化学对相应的 h1JOH⋅⋅⋅F 值具有至关重要的影响，如顺-和反-4-氟戊烷-2-醇（6.6 和 1.9Hz）所示。 OH⋅⋅⋅F IMHBs 的大小及其对整体分子构象、氟化基序和烷基取代水平的强烈依赖性，通过量子化学计算得到了合理化。对于给定的烷基链，“屏蔽规则”适用于 OH⋅⋅⋅F IMHB 能量。令人惊讶的是，预测的 OH⋅⋅⋅F IMHB 能量仅比相应的 OH⋅⋅⋅OMe 弱一些。这些结果为脂肪醇氟化的影响提供了新的见解，为合理的药物设计提供了有吸引力的前景。
Fluorination is commonly exercised in compound property optimization. However, the influence of fluorination on hydrogen-bond (HB) properties of adjacent functional groups, as well as the HB-accepting capacity of fluorine itself, is still not completely understood. Although the formation of OH⋅⋅⋅F intramolecular HBs (IMHBs) has been established for conformationally restricted fluorohydrins, such interaction in flexible compounds remained questionable. Herein is demonstrated for the first time—and in contrast to earlier reports—the occurrence of OH⋅⋅⋅F IMHBs in acyclic saturated γ-fluorohydrins, even for the parent 3-fluoropropan-1-ol. The relative stereochemistry is shown to have a crucial influence on the corresponding h1JOH⋅⋅⋅F values, as illustrated by syn- and anti-4-fluoropentan-2-ol (6.6 and 1.9Hz). The magnitude of OH⋅⋅⋅F IMHBs and their strong dependence on the overall molecular conformational profile, fluorination motif, and alkyl substitution level, is rationalized by quantum chemical calculations. For a given alkyl chain, the “rule of shielding” applies to OH⋅⋅⋅F IMHB energies. Surprisingly, the predicted OH⋅⋅⋅F IMHB energies are only moderately weaker than these of the corresponding OH⋅⋅⋅OMe. These results provide new insights of the impact of fluorination of aliphatic alcohols, with attractive perspectives for rational drug design.